等差数列an满足a1+a2+...+a101=303 则a3+a99=

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等差数列an满足a1+a2+...+a101=303 则a3+a99=
等差数列an满足a1+a2+...+a101=303 则a3+a99=

等差数列an满足a1+a2+...+a101=303 则a3+a99=
等差数列an
S101=(a1+a101)/2*101=303
∴a1+a101=6
1+101=3+99
∴a3+a99=a1+a101=6

（a1+a101）乘101乘二分之一=303，a1+a101=6，所以a2+a100=6，所以a3+a99=6

a1+a2+。。。+a101=303=s101=101×（a1+a101)÷2=101×（a3+a99)÷2
得a3+a99=6
用了等差数列和的公式和等差数列的性质，因为等差数列有一个性质，如果1+101=3+99，则a1+a101=a3+a99

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